Copper spots in gold coins

[Stuh]

I’m confused on this subject… I always thought that copper spots were essentially an ‘unmixed’ portion of copper inside an alloyed gold coin (i.e. less than 24k) - doesn’t affect the coin value particularly, as I understand it. Sometimes they are spots, but also sometimes stripes / smears if the copper was smooshed about during rolling etc.
 

However, there’s a sales thread currently up that has pretty big copper spots on some Queens beasts coins, which are four 9’s purity, so how do they end up with copper spots if there’s no copper in the coin to begin with? Am I missing something in my understanding? Just looking to learn here 👍

Thanks!

[Petra]

6 minutes ago, Stuh said:

I’m confused on this subject… I always thought that copper spots were essentially an ‘unmixed’ portion of copper inside an alloyed gold coin (i.e. less than 24k) - doesn’t affect the coin value particularly, as I understand it. Sometimes they are spots, but also sometimes stripes / smears if the copper was smooshed about during rolling etc.
 

However, there’s a sales thread currently up that has pretty big copper spots on some Queens beasts coins, which are four 9’s purity, so how do they end up with copper spots if there’s no copper in the coin to begin with? Am I missing something in my understanding? Just looking to learn here 👍

Thanks!

There is copper in all of the gold coins. Research in China has suggested that it could also be silver which is quite often found in gold reacting to sulphur in the atmosphere.

[Stuh]

4 minutes ago, Petra said:

There is copper in all of the gold coins. Research in China has suggested that it could also be silver which is quite often found in gold reacting to sulphur in the atmosphere.

Thank you 🙏 I’m guessing that the 1 part out of 10,000 (in a four nines coin) is what’s causing it then, whether that’s copper or silver. I don’t mind copper spots myself - a bit of character!

[MBTPSilver]

Yes, even 999 or 9999 gold still has some other metals which can find their way to the surface. If we say 31.1 grams for a troy ounce, that would be 0.00311 grams of other metals, in 9999 gold, or 0.0311 grams in 999 gold.

There can also be extra materials that find their way onto the die stamps occasionally, pretty difficult to keep a completely 100% sterile production facility. Tend to see it with bars in particular, but the odd coin shows up now and then too.

[Stuh]

43 minutes ago, MBTPSilver said:

Yes, even 999 or 9999 gold still has some other metals which can find their way to the surface. If we say 31.1 grams for a troy ounce, that would be 0.00311 grams of other metals, in 9999 gold, or 0.0311 grams in 999 gold.

There can also be extra materials that find their way onto the die stamps occasionally, pretty difficult to keep a completely 100% sterile production facility. Tend to see it with bars in particular, but the odd coin shows up now and then too.

Thank you, that makes sense! Tiny quantities of ‘impurities’ but enough to matter then!